This project proposes to analyze statistically the spontaneous activity of single neurons in the nucleus ventralis posterior, medialis and lateralis of the thalamus during natural sleep and wakefulness in behaving monkeys. We propose to identify those ventral basal thalamic neurons which are responsive to thermal changes of the skin and to test the responsiveness of these thermoreceptor thalamic cells not only to induced and spontaneous changes in skin temperature but also to other forms of natural peripheral stimulation. These studies will be performed in animals chronically prepared for extracellular microelectrode recording in the ventral-posterior complex of the thalamus, for EEG, EMG and EOG recordings and, in selected experiments, for measurements of skin and brain temperature and for thermal stimulation of the skin, all according to the techniques previously developed in this laboratory. In order to avoid the depressant effects of anesthetic agents and to study the linkage between thermoregulation and behavior I propose to study thalamic somatosensory neurons, particularly thalamic thermoreceptors, in behaving monkeys.